The human heart has a number of valves for maintaining the flow of blood through the body in the proper direction. The major valves of the heart are the atrioventricular (AV) valves, including the bicuspid (mitral) and the tricuspid valves, and the semilunar valves, including the aortic and the pulmonary valves. When healthy, each of these valves operates in a similar manner. The valve translates between an open state (that permits the flow of blood) and a closed state (that prevents the flow of blood) in response to pressure differentials that arise on opposite sides of the valve.
A patient's health can be placed at serious risk if any of these valves begin to malfunction. Although the malfunction can be due to a variety of reasons, it typically results in either a blood flow restricting stenosis or a regurgitation, where blood is permitted to flow in the wrong direction. If the deficiency is severe, then the heart valve may require replacement.
Substantial effort has been invested in the development of replacement heart valves, most notably replacement aortic and mitral valves. Replacement valves can be implanted percutaneously by way of a transfemorally or transapically introduced catheter, or can be implanted directly through open heart surgery. The replacement valves typically include an arrangement of valve leaflets that are fabricated from porcine tissue. These tissue leaflets are highly distensible or stretchable. Other replacement valves have been proposed where the leaflets are artificial polymeric structures. In both cases, the leaflets are often maintained in position by a stent or support structure that has a relatively high rigidity (in the case of open heart replacement valves) or expands into or is fixable in a highly rigid state (in the case of transcatheter valves) to provide maximum support for the leaflets. However, these highly rigid support structures are generally passive structures that, beyond support, provide little or no active benefit to the operation of the valve itself in controlling flow.
For these and other reasons, needs exist for improved prosthetic valves.